Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $181.60   6.866%   $194.0687   $194.07   $194.05   $194.10  
  Purchase #2 $193.54   10.717%   $214.2817   $214.28   $214.30   $214.30  
  Purchase #3 $198.82   9.551%   $217.8093   $217.81   $217.80   $217.80  
  Purchase #4 $95.81   13.321%   $108.5729   $108.57   $108.55   $108.60  
  Purchase #5 $224.57   9.102%   $245.0104   $245.01   $245.00   $245.00  
  Purchase #6 $216.81   3.263%   $223.8845   $223.88   $223.90   $223.90  
  Purchase #7 $80.67   4.188%   $84.0485   $84.05   $84.05   $84.00  
  7 purchase totals = $1,191.82       $1,287.6760   $1,287.67   $1,287.65   $1,287.70